geli - selecting cipher

[Michael Sierchio]

On Wed, Jul 25, 2012 at 11:57 AM, Wojciech Puchar
<wojtek at wojtek.tensor.gdynia.pl> wrote:
> i need high speed disk encryption (many disks running in parallel, lots of

> I'm not cryptography expert, is CBC somehow "less secure", and if so is it
> really a problem?

XTS-AES is a standard devised specifically for disk encryption - it
supports operations on sectors that aren't divisible by the cipher
block size.

See  http://en.wikipedia.org/wiki/Disk_encryption_theory#XEX-based_tweaked-codebook_mode_with_ciphertext_stealing_.28XTS.29

I personally would be fine with AES-CTR mode, since I don't see the
need to defend against the mythical "strong" adversary who can write
arbitrary bits to unused sectors and then ask to have them decrypted.
AES-CTR doesn't (by itself) have any integrity check.

AES-CBC is fine, but the ciphertext is larger than the plaintext.

- M